Caliper Rebuild

[Kevin]

I had noticed some very strange softness in the front break -- only while WALKING backwards with the front wheel full right -- the front brake would occasionally go full to the bar. Not good. It would immediately come back strong when I straightened the wheel.

A couple of days ago I re-bled the brakes (with speed bleeders). They looked perfect with no bubbles at all, but the problem remained. The pads were about half worn from a change about 2 years ago and I had another set, so I thought I would replace them as long as I'm here. Then again, re-bled the brake lines and again not a single bubble. Now I can pump the brakes up hard, but if I move 10 feet forward or back (with the front wheel pointing any direction), I get zero pressure again. And again, it will pump right up. I did pull the pads to double-check all was well, and it appears it is done properly.

The master cylinder diaphragm appears intact. I see absolutely no fluid leaking anywhere. My only conclusion is that I have a seal leak in one of the calipers. Replacing caliper seals would be a new task for me. I would consider myself a 4 (out of 10) when it comes to wrenching (do my own oil, brake pads, EFI synch, plugs, rear spline, tires, etc.) -- but if this is a major job I might be better off buying a new caliper assembly compared to paying stealer labor rates to replace the seals. I have a service manual here somewhere but I would have to search for it.

Is there any way to determine which caliper is leaking? How difficult a job is it to replace the seals within a caliper? And finally, what's your favorite price-leading Internet parts store?

Thanks in advance!

Kevin <><<

'03 FJR - 22k miles

 

[kulwen]

Here is a link to a unrelated brake problem I had, might give you some ideas.

Link

 

[No One]

I had noticed some very strange softness in the front break -- only while WALKING backwards with the front wheel full right -- the front brake would occasionally go full to the bar. Not good. It would immediately come back strong when I straightened the wheel.
A couple of days ago I re-bled the brakes (with speed bleeders). They looked perfect with no bubbles at all, but the problem remained. The pads were about half worn from a change about 2 years ago and I had another set, so I thought I would replace them as long as I'm here. Then again, re-bled the brake lines and again not a single bubble. Now I can pump the brakes up hard, but if I move 10 feet forward or back (with the front wheel pointing any direction), I get zero pressure again. And again, it will pump right up. I did pull the pads to double-check all was well, and it appears it is done properly.

The master cylinder diaphragm appears intact. I see absolutely no fluid leaking anywhere. My only conclusion is that I have a seal leak in one of the calipers. Replacing caliper seals would be a new task for me. I would consider myself a 4 (out of 10) when it comes to wrenching (do my own oil, brake pads, EFI synch, plugs, rear spline, tires, etc.) -- but if this is a major job I might be better off buying a new caliper assembly compared to paying stealer labor rates to replace the seals. I have a service manual here somewhere but I would have to search for it.

Is there any way to determine which caliper is leaking? How difficult a job is it to replace the seals within a caliper? And finally, what's your favorite price-leading Internet parts store?

Thanks in advance!

Kevin <><<

'03 FJR - 22k miles

If you have a leak that would make a performance difference you should see some seeping if you take the caliper off the bike and remove the pads..... The piston removal is easy but DO NOT scrach the piston(s)... Removing and reinstalling new 'rubbers' the seals is really easy... pop out / pop in... make sure you pre lube the new seals and and the cleaned pistons with new brake fluid. A good Yamaha joint to get a good deal on parts is www.stadiumyamaha.com Ask for Robert or Gary........ There are also a ton of 'How too" on the net

 

[El Toro]

You can't really judge whether you've got air in your line by watching bubbles. It is possible for a bit of air to catch in a high point of a line, and sit there creating a problem, and you can't see it.... but you sure can feel it with the spongy lever or pedal.

Its tricky to get a good bleed. Sometimes it helps to reposition the bike. If it was on the center stand, put it on the side stand, for example, during the bleeding.

Then on some bikes there are intermediate bleed points. I haven't looked at the FJR, but its important to do the bleeding in the appropriate order.

If you're not seeing fluid leaking, chances are you've still got some air stuck somewhere, and it won't come out except by bleeding it out.

 

[radman]

Sounds to me to be more likely the master cylinder. Or low fluid level-you mention it first occurred with the bars full right-direction of travel is irrelevant. If you uncover the reservoir to cylinder feed hole, and pump, yer ******. You've introduced air into the system, and only a hard core bleed is going to restore the system. ABS makes it even more difficult. Do a hard core gravity bleed, starting with the caliper furthest from the cylinder, ie: left, then a pressure bleed, then wrap a bungie around the lever and grip with the lever fully depressed, as in hard on, and let sit overnight. You'll have brakes.

 

[luvtoride]

I had a similar experience except for the fact that I was moving... as in riding when my front brakes would lose pressure. It turned out that it was the wheel bearings. The bad bearings were allowing the wheel to move (in the way that it's not supposed to) & open up the calipers... thus requiring pumping to get the calipers to be touching the rotor once again. Once my wheel moved it opened the calipers back open starting the whole process over again.

This is very well not your problem but thought that I'd mention it.... just in case.

 

[Bustanut joker]

heh heh, heh heh....... He said hard on Beavus... :lol:

:jester:

 

[Kevin]

This is just weird. In fact, it's even worse that I originally described. I can pump the brakes up hard -- can only pull them half-way back which I consider normal. If I walk backwards with the bar straight, all remains OK. But if I walk back or forward even a few feet, moving the bar full left and full right -- I have ZERO pressure, all the way back to the bar with absolutely no resistance. That doesn't feel like an air "bubble" to me.

I pulled each caliper (still connected to the brake line) and removed the pads. All 8 pistons appear to be working. There was not a hint of any fluid or any weird substance on the pistons. The speed bleaders are tight. There is no apparent loss of fluid in the master cylinder. I don't see any fluid anywhere it doesn't belong. I bled them a third time (something I've done dozens of times in the past without a problem) and again all looks good -- no air in the tubing at the speed bleeder, no air at the master cylinder. The master cylinder is (and has been) right at the full line -- I don't see any way that air is getting introduce there.

I bled each side with the bar full left, full right, and even bungied the cord to the bar for 24 hours. No change.

I'm at a loss. I can start replacing parts, but that might get expensive fast. Logically, air is getting re-introduced but there is no apparent fluid leak. My best guess is the lines themselves (which are original and due for replacement anyway) or the bolts/seals where they connect. Maybe replacement lines are in order?

Thanks again!

Kevin

:dribble: :dribble: :dribble: :dribble:

 

[S76]

But if I walk back or forward even a few feet, moving the bar full left and full right -- I have ZERO pressure, all the way back to the bar with absolutely no resistance. That doesn't feel like an air "bubble" to me.

When you get to this condition were you have no brake pressure, can you just pump the lever a few times and regain the pressure? And then is it OK as long as you don't turn the bars?

Unless I am misreading this it sounds like when you turn the bars the brake discs may be pushing the pads and pistons back, so then you have to pump it up again. If that is the case it sounds like what Heidi was saying. Maybe you have bad wheel bearings allowing the front wheel to rock? Or maybe the front wheel is loose?

Can you have someone turn the bars left and right while you observe the discs for movement in the caliper? Jack the front wheel off the ground and check for play in the wheel and disc assembly.

 

[radman]

Well, the only thing that makes sense then is wheel movement laterally, as mentioned before. A test would be to move the bike as you have done, then once you have no lever pressure, see if you can pump up the brakes and get a firm lever back, while the fork is still turned. You've had the wheel off, I assume. Possible you left one of the spacers out? And, it could still be needing a master rebuild, parts about $30. It's possible for the cups to leak air, not fluid. Every time you release the lever, a low pressure is built in the bore-the reservoir allows fluid to refill the bore at this time. If the back seals are in poor shape, air can get past the seal and raise hell.

Set 2 is the master kit. I can think of no other causes for such a problem. Fluid leaks are self evident. Another possibility is in the calipers, but pretty rare I think. The caliper seal is designed to maintain a certain shape, in that it retracts the piston into the bore under normal conditions after a brake application. If the bore is corroded, and the seal old and tired, it can do weird things such as you describe, but the turning thing is just out there. The bike is old enough, and the problem strange enough, that were it mine, a master kit and caliper kits would be part of the solution. Another possible is a brake hose with an internal rupture. The inner tube can fracture, allowing fluid to leak into the space between the inner and outer tube-this can be spotted by careful inspection of the hoses while applying the brake-look for a swelling that grows with application, diminishes on release. Again, since the hoses move with the fork, that it only happens on full lock messes with the scenario, but then?????

Looking at Frank, the master sits level when the fork is straight, at an angle at lock in either direction. I still think the problem is in the master, cost ya $30 and an hour or two to find out. It's the only real fluid part of the system I can think of that could cause the symptoms.

Another thought-is there a lot of sediment or debris in the reservoir? This could, in theory, block the hole to the master bore at times, not so much at angles, but then again, ??????

 

[spalkin]

I didn't see where you checked the fluid level in the reservoir. That's the only thing I can think of that could cause the lever to pull all the way to the bar but be able to be pumped back up.

Interesting problem.

 

[squeezer]

I think luvtoride and radman are on to something with the lateral wheel movement pushing the calipers apart. Getting the front wheel in the air and checking for movement will only take you a couple of minutes and it's free.

 

[Kevin]

When you get to this condition were you have no brake pressure, can you just pump the lever a few times and regain the pressure? And then is it OK as long as you don't turn the bars?

Exactly.

I'll check the wheel for play again -- did that once, but I wasn't looking specifically for the calipers being pushed in.

AND, I'll rebuild the master cylinder. Both wonderful suggestions. I'll advise after the parts arrive.

I am in your debt.

Kevin

 

[luvtoride]

Can you have someone turn the bars left and right while you observe the discs for movement in the caliper? Jack the front wheel off the ground and check for play in the wheel and disc assembly.

Ya know Bob, if I remember correctly, my mechanic couldn't see the play in the wheel when my bearings were caputo. It was suspected that my bearings were the problem (because of Jeff Ashe's over the phone diagnosis) & it was not apparent until my mech broke the front wheel loose & stuck his finger on the bearings.

One of the bearings was actually gone out of the race. Isn't that nice!!!

 

[S76]

One of the bearings was actually gone out of the race. Isn't that nice!!!

Gee that is flat out scary! I'm changing mine out this winter.

I probably go through more "parts that never failed" than anyone. Too many years of working on aircraft I guess. If it is even remotely suspect or if it has a bad history with other people it gets changed out. This year will see all wheel bearings, brake pads, all fluids, cam chain and tensioner, valve adjust, ignition switch mod. battery etc. "This bike has cost me a fortune in parts.... and it has never broke down.

 

[HotRodZilla]

heh heh, heh heh....... He said hard on Beavus... :lol:
:jester:

Don't get all excited. He wasn't talking to YOU. Put the vaseline down and step away............. :lol:

 

[Bustanut joker]

heh heh, heh heh....... He said hard on Beavus... :lol:
:jester:

Don't get all excited. He wasn't talking to YOU. Put the vaseline down and step away............. :lol:

Ha jokes on you junior!! I quit usin' vasoline. It made my hand to slippery.

It made fast getaways from the widow peepin' at the old folks home damn near impossible. After a close encounter with yer comrads it's Ky for me now

:jester:

 

[Kevin]

DING DING DING DING! We have a winner! And the answer is......................front bearings, of course.

I pumped the brakes hard. Jacked up the front. Tire spins fine -- no noise. Checked the brakes -- still hard. Sat on my butt facing the tire, tried my best to forcibly push the wheel left/right against the forks, spun the wheel 10 degrees, repeat until all the way around. I *thought* maybe there was a bit of wiggle, but then again this is a rather unique perspective of my bike so it is hard to tell -- I'm not sure if there is a "normal" here, plus it is very subtle. It's not like it is clearly moving out of true. But I tried the brakes -- NOTHING!!

I pulled the tire and took it to the dealer for bearings (another job I haven't learned how to do). Once pulled, the bearings were clearly shot and some were even missing -- I am surprised that is possibly stayed as straight as it did on the bench test! And then I thought about how I was just riding on those things a week ago! UGH!! $35 and an hour later I put the tire back on. Everything is PERFECTO!! I even rode to work today in the 30-degree weather. Man, that felt good!

Thanks to Luv for having the idea first (I think). But also to Rad who explained it -- at first, I didn't understand the connection between the bearings and the calipers!

I'm wondering now if bearings should be replaced with every tire change? Or at LEAST every other tire change!

Grape Ne-Hi's are on me -- drinks all around! I am in your debt!

Kevin

https://KevinArnold.us/

 

[luvtoride]

I'm glad that you got it figured out... & as for a grape nehi? Yeah, well I don't think so. This woman is more expensive than that! I'll have a bud light, please. :blush:

Oh, something else that I learned about wheel bearings. They rarely go bad. No need to change them every tire change.

My problem arose when I went ditch surfing on my bike about a year & 1/2 ago. The insurance company replaced the front rim since the gravel in the ditch tore it up cosmetically. I had all wheel components swapped over to the new wheel... also putting new bearings into it. (I have heard that you NEVER reuse old bearings) Well, I suspect that my mechanic's helper put the new bearings in & I also suspect that he damaged one of the races while pressing them into the rim.

Live & learn. So, glad that I could help out, Heidi